1 The Characteristics of Equilibria of SlightlySolubleIonicCompounds1-1.The Characteristics : heterogeneous equilibriaBaSO4 (s) 台 Ba2+ (aq)+ SO.2- (aq)Making the assumption of complete dissociationwe can state that for slightly soluble ionic compoundsequilibrium exists between solid solute and dissolved ions
6 1 The Characteristics of Equilibria of Slightly Soluble Ionic Compounds 1-1. The Characteristics ： heterogeneous equilibria BaSO4 (s) Ba2+ (aq)+ SO4 2- (aq) Making the assumption of complete dissociation, we can state that for slightly soluble ionic compounds, equilibrium exists between solid solute and dissolved ions
1-2. The Solubility-Product Constant---K.p(溶度积常数IEBaSO4 (s) 台 Ba2+ (aq)+ SO.2- (aq)SSKsp=[Ba2+[ SO,2]= S2Generally A.B,mAn+ + nBm-nsmsKs=[A"+]"[B"-]"=[mS]"[nS]=mmn"Sm+n
7 1-2. The Solubility-Product Constant - Ksp(溶度积常数) BaSO4 (s) Ba2+ (aq)+ SO4 2- (aq) t e S S Ksp = [Ba2+ ][ SO4 2- ] = S 2 Generally AmBn mAn+ + nBmt e mS nS Ksp = [An+] m[ Bm- ] n = [mS] m[nS ] n = mm n n S m+n
1-3. Comparison of K.n and S (molar solubility)Tablel.K.nand S of someIonic CompoundsKpCompositionMolecularS(mol/L)patternFormula1.8 × 10-10AB1.3 × 10-5AgCl5.0 × 10-137.1 × 10-7ABAgBr2.0 × 10-127.9 × 10-5A,BAg,CrO46.7 × 10-502.6 × 10-17A,BAg,SFor molecules with the same pattern, the higher its Ksp,the higher its SFor molecules with different patterns, higher Ksn doesn't mean higher S
8 1-3. Comparison of Ksp and S (molar solubility) Table1. Ksp and S of some Ionic Compounds Composition pattern Molecular Formula Ksp S(mol/L) AB AgCl 1.8 10-10 1.3 10-5 AB AgBr 5.0 10-13 7.1 10-7 A2B Ag2CrO4 2.0 10-12 7.9 10-5 A2B Ag2 S 6.7 10-50 2.6 10-17 For molecules with the same pattern, the higher its Ksp, the higher its S. For molecules with different patterns, higher Ksp doesn’t mean higher S
-The solubility-product Ksn and the molar solubility S.both express the soluble ability of a compound.As formolecules with the same pattern, the higher its Ksp, thehigher its S.But for molecules with different patternshigherK.n doesn't mean higher S.-Another point is that the Ksn is a function of thetemperature, it has nothing to do with ionsconcentrations, while S changes with the ionsconcentrations
9 ▪The solubility-product Ksp and the molar solubility S, both express the soluble ability of a compound. As for molecules with the same pattern, the higher its Ksp, the higher its S. But for molecules with different patterns, higher Ksp doesn’t mean higher S. ▪Another point is that the Ksp is a function of the temperature, it has nothing to do with ions’ concentrations, while S changes with the ions’ concentrations